Enforcement of semiconductor structure regularity for localized transistors and interconnect

ABSTRACT

A global placement grating (GPG) is defined for a chip level to include a set of parallel and evenly spaced virtual lines. At least one virtual line of the GPG is positioned to intersect each contact that interfaces with the chip level. A number of subgratings are defined. Each subgrating is a set of equally spaced virtual lines of the GPG that supports a common layout shape run length thereon. The layout for the chip level is partitioned into subgrating regions. Each subgrating region has any one of the defined subgratings allocated thereto. Layout shapes placed within a given subgrating region in the chip level are placed in accordance with the subgrating allocated to the given subgrating region. Non-standard layout shape spacings at subgrating region boundaries can be mitigated by layout shape stretching, layout shape insertion, and/or subresolution shape insertion, or can be allowed to exist in the final layout.

CLAIM OF PRIORITY

This application is a divisional application under 35 U.S.C. 121 of prior U.S. application Ser. No. 12/363,705, filed Jan. 30, 2009, and entitled “Enforcement of Semiconductor Structure Regularity for Localized Transistors and Interconnect,” which claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 61/024,980, filed Jan. 31, 2008, entitled “Enforcement of Semiconductor Structure Regularity for Localized Transistors and Interconnect.” The disclosure of each above-identified patent application is incorporated herein by reference.

BACKGROUND

FIG. 1 shows a typical CMOS transistor configuration, in accordance with the prior art. In the example of FIG. 1, a preferred direction for an interconnect level (metal-1) is parallel to that for gate electrode (gate) wires, as seen for metal-1 wire 105 and gate wire 103. Gate wire 103 overlaps a diffusion shape 101, forming a transistor with a source or drain (S/D) node that is connected to metal-1 wire 105 by a contact 106. Wire 105 requires a non-rectangular shape, i.e., a shape with a bend, to allow it to overlap a contact 102 which connects to a gate wire 107. FIG. 1 also shows a gate electrode wire 104 that requires a bend to overlap a gate contact 108, which connects to a metal-1 wire 109.

The typical CMOS transistor configuration of FIG. 1 illustrates a number of features that may increase manufacturing difficulty. For example, contacts for S/D and gate connections are not aligned, gate and metal wire widths are variable, spacing between wire shapes is variable, wire center lines are variably spaced apart, and a ratio of filled to non-filled space for gate and metal-1 levels is variable. These features may cause parametric and defect yield loss in advanced semiconductor processes due to associated lithographic effects, CMP (chemical mechanical planarization) dishing, and/or other manufacturing imperfections. Therefore, it is of interest to define a semiconductor device layout methodology that accounts for layout characteristics which adversely affect manufacturability.

SUMMARY

In one embodiment, a method is disclosed for defining a layout for a portion of a given semiconductor chip level. The method includes an operation for defining a preferred routing direction for a given chip level. The method also includes an operation for identifying each contact level related to the given chip level, wherein each contact level includes at least one interfacing contact defined to physically connect with a structure corresponding to a layout shape to be placed in the given chip level. An operation is then performed to define a global placement grating (GPG) for the given chip level to include a set of parallel and evenly spaced virtual lines. At least one virtual line of the GPG is positioned to intersect each interfacing contact within each contact level related to the given chip level. A determination is then made as to whether a perpendicular spacing between adjacent virtual lines of the GPG provides for enforcement of layout shape pattern regularity within the given chip level as necessary to ensure manufacturability of layout shapes within the given chip level. If it is determined that the perpendicular spacing between adjacent virtual lines of the GPG is acceptable, the method proceeds with placement of layout shapes in alignment with the GPG for the given chip level. However, if it is determined that the perpendicular spacing between adjacent virtual lines of the GPG is not acceptable, the method proceeds with an operation for adjusting placement of one or more interfacing contacts within one or more contact levels related to the given chip level. The method then reverts back to the operation for defining the GPG for the given chip level.

In another embodiment, a method is disclosed for defining a layout for a portion of a given semiconductor chip level. In the method, a GPG is defined for a given chip level. The GPG is defined by a set of parallel and evenly spaced virtual lines. The method includes identifying all connection lines within the GPG. A connection line is a virtual line of the GPG that is spatially coincident with a virtual line of a related contact level. A subgrating is defined for the given chip level as a set of evenly spaced connection lines, such that a spacing between adjacent connection lines in the subgrating is at least as large as a minimum spacing required to support a common run length of layout shapes on the adjacent connection lines in the subgrating. Definition of subgratings is repeated until each connection line within the GPG is associated with at least one subgrating. The method further includes placement of layout shapes in alignment with the defined subgratings, such that each layout shape is associated with any one subgrating.

In another embodiment, a method is disclosed for defining a layout for a portion of a given semiconductor chip level. The method includes an operation for defining a GPG for a given chip level. The GPG is defined by a set of parallel and evenly spaced virtual lines. All connection lines within the GPG are identified. A connection line is a virtual line of the GPG that is spatially coincident with a virtual line of a related contact level. The method also includes an operation for defining a subgrating for the given chip level as a set of evenly spaced connection lines, such that a spacing between adjacent connection lines in the subgrating is at least as large as a minimum spacing required to support a common run length of layout shapes on the adjacent connection lines in the subgrating. The operation for defining the subgrating is repeated until each connection line within the GPG is associated with at least one subgrating. The layout for the given chip level is then partitioned into a number of subgrating regions. Each subgrating region is defined as a contiguous area within the layout for the given chip level. Subgratings are allocated to the number of subgrating regions such that only one subgrating is allocated to any one subgrating region. The method further includes an operation for placing functional layout shapes for the given chip level in alignment to the subgratings allocated to the subgrating regions. Following placement of the functional layout shapes, a non-standard spacing is identified within the layout of the given chip level. The method includes an operation for resolving the non-standard spacing so as to ensure manufacturability of structures corresponding to the functional layout shapes.

Other aspects and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a typical CMOS transistor configuration, in accordance with the prior art;

FIG. 2 shows a portion of a layout for a given chip level in which a GPG is defined and in which linear layout shapes are placed in alignment with the GPG, in accordance with one embodiment of the present invention;

FIG. 3A shows an example in which a subgrating pitch results in a ratio of side-to-side spacing to layout shape width that is too large to maintain sufficient shape density for proper manufacturing;

FIG. 3B shows a modification of the layout of FIG. 3A in which a subresolution shape is used to mitigate the unacceptably large side-to-side spacing to width ratio, in accordance with one embodiment of the present invention;

FIG. 4 shows an example layout in which a GPG is used to place layout shapes for gate electrode wires, interconnect wires, diffusion contacts, and gate contacts, in accordance with one embodiment of the present invention;

FIG. 5 shows an extension of the exemplary layout of FIG. 4 in which a number of subgrating regions are defined in various chip levels, in accordance with one embodiment of the present invention;

FIG. 6 shows an example layout that illustrates subgrating use among different vertically stacked chip levels, in accordance with one embodiment of the present invention;

FIG. 7 shows an example layout in which a multi-level orthogonally routed connection is used to connect wires in a same chip level that cannot have a common run length, in accordance with one embodiment of the present invention;

FIG. 8 shows another example layout in which a multi-level orthogonally routed connection is used to connect wires in a same chip level that cannot have a common run length, in accordance with one embodiment of the present invention;

FIG. 9A shows an example layout that illustrates the occurrence of a non-standard spacing at an interface between adjacent subgrating regions, in accordance with one embodiment of the present invention;

FIG. 9B shows a layout shape stretching technique for mitigating a non-standard spacing introduced at subgrating region borders that lie parallel to the routing direction, in accordance with one embodiment of the present invention;

FIG. 10A shows an example layout that illustrates the occurrence of a non-standard spacing at an interface between adjacent subgrating regions, when the layout shape stretching technique of FIG. 9B is blocked, in accordance with one embodiment of the present invention;

FIG. 10B illustrates use of a subresolution shape to mitigate a non-standard spacing at an interface between adjacent subgrating regions, when the layout shape stretching technique of FIG. 9B is blocked, in accordance with one embodiment of the present invention;

FIG. 11 shows an exemplary layout in which a layout shape is stretched to overlap multiple contacts and/or vias, in accordance with one embodiment of the present invention;

FIG. 12 shows another example in which layout shapes are stretched to overlap multiple contacts and/or vias, in accordance with one embodiment of the present invention;

FIG. 13 shows an example in which layout shapes are extended relative to a contact and/or via so as to accommodate design requirements, in accordance with one embodiment of the present invention;

FIG. 14 shows a flowchart of a method for defining a layout for a portion of a given semiconductor chip level, in accordance with one embodiment of the present invention;

FIG. 15A shows a flowchart of a method for defining a layout for a portion of a given semiconductor chip level, in accordance with one embodiment of the present invention;

FIG. 15B shows an expanded view of operation 1509 of FIG. 15A, in accordance with one embodiment of the present invention;

FIG. 15C shows an extension of the method of FIGS. 15A-15B, in accordance with various embodiments of the present invention; and

FIG. 16 shows a flowchart of a method for defining a layout for a portion of a given semiconductor chip level, in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.

Within the context of the present invention, a global placement grating (GPG) is defined by a set of parallel and evenly spaced virtual lines extending across a semiconductor chip (“chip” hereafter) level. The even, i.e., equal, perpendicular spacing between adjacent virtual lines of a GPG is referred to at the GPG pitch (GPGP). Layout shapes within a portion of a given chip level can be placed in accordance with the GPG of the given chip level. For example, layout shapes within a portion of a given chip level may be centered upon or in some way indexed to virtual lines of the GPG of the given chip level. Also, the virtual lines of the GPG of a given chip level are oriented to extend in a preferred routing direction of the given chip level, wherein the preferred routing direction corresponds to a direction in which layout shapes are defined to extend.

In one embodiment, the layout shapes placed in accordance with the GPG are defined as linear layout shapes. Each linear layout shape has a substantially rectangular cross-section when viewed in an as-drawn state. In one embodiment, the linear layout shape does allow for small deviations from the rectangular cross-section. For example, a linear layout shape may include one or more expanded regions along its rectangular cross-section length so as to accommodate contact placements and connections thereto. In another embodiment, strict adherence to a substantially rectangular cross-section may be specified for the linear layout shapes. It should be understood that a degree of rectangularity of the linear layout shapes can vary between embodiments, depending on the requirements for design and layout of a particular embodiment. In one embodiment, each linear layout shape placed in a portion of a given chip level is placed such that a length of its substantially rectangular cross-section is parallel with the GPG of the given chip level. Therefore, in this embodiment, the linear layout shapes extend in the preferred routing direction of the given chip level which is parallel to the virtual lines of the GPG.

Also, in one embodiment, each linear layout shape is initially placed in a centered manner such that its centerline extending in the preferred routing direction is substantially centered upon a virtual line of the GPG. It should be understood, however, that following initial placement of a given layout shape in the centered manner, a width of the given layout shape may be adjusted, or the given layout shape may be stretched in its width direction, such that a final version of the given layout shape is no longer centered upon a virtual line of the GPG.

FIG. 2 shows a portion of a layout for a given chip level in which a GPG is defined and in which linear layout shapes are placed in alignment with the GPG, in accordance with one embodiment of the present invention. The GPG of FIG. 2 is defined by virtual lines 200-209, with adjacent virtual lines evenly spaced at the GPG pitch (GPGP). The virtual lines 200-209 of the GPG extend in the preferred routing direction of the given chip level. FIG. 2 depicts layout shapes as shaded rectangular shapes. The layout shapes within the portion of the given chip level are defined as linear layout shapes and are placed so as to be substantially centered upon a virtual line of the GPG.

FIG. 2 further illustrates concepts of the present invention referred to as subgrating and subgrating regions. A subgrating is defined as a set of evenly spaced GPG lines having a subgrating pitch that is an integer multiple of the GPG pitch. A subgrating region is defined as a layout area of a portion of a given chip level within which layout shapes are placed according to a single subgrating. In one embodiment, a subgrating is defined to accommodate a common run length of layout shapes having a specified uniform width, wherein the common run length refers to side-by-side existence of layout shapes on adjacent subgrating virtual lines.

FIG. 2 shows by way of example five separate subgrating regions 220-224, where a periphery of each subgrating region 220-224 is delineated by bold solid lines. Each of subgrating regions 220-224 is associated with a particular subgrating. The subgrating within each subgrating region 220-224 is delineated by bold dashed lines. The subgratings for each of subgrating regions 220 and 224 include each virtual line of the GPG (GPG virtual lines 200-206 for subgrating region 220, and GPG virtual lines 207-209 for subgrating region 224). The subgrating for subgrating region 221 includes every other even numbered virtual line of the GPG (GPG virtual lines 200, 202, 204, 206), such that the corresponding subgrating pitch is 2*GPGP. The subgrating for subgrating region 222 includes every other odd numbered virtual line of the GPG (GPG virtual lines 201, 203, 205, 207, 209), such that the corresponding subgrating pitch is 2*GPGP. The subgrating for subgrating region 223 includes every third virtual line of the GPG, (GPG virtual lines 201 and 204), such that the corresponding subgrating pitch is 3*GPGP.

As shown in FIG. 2, linear layout shapes are initially placed in a centered manner on the subgrating of the subgrating region in which the linear layout shape is placed. Also, it should be appreciated from the example of FIG. 2 that layout shapes of uniform width placed in accordance with the same subgrating can have a common run length. Also, layout shapes that are placed on the same virtual line of the GPG in adjacent subgrating regions may, if necessary, be extended through the interface between the adjacent subgrating regions so as to combine and form single contiguous layout shape that spans the interface between the adjacent subgrating regions. For example, FIG. 2 shows layout shapes 250A and 250B extending through the interface between adjacent subgrating regions 222 and 224 so as to form a single layout shape 250.

It should be understood that a subgrating region is defined as a contiguous area within a layout of a portion of a given chip level in which layout shapes are aligned to a common subgrating. It should also be understood that a subgrating region can be defined to have an arbitrary shape. However, in one embodiment, an effort is made to define subgrating regions such that a minimal number of boundary segments are used to define a periphery of each subgrating region. Also, in one embodiment, when possible, layout shapes having related functions are grouped together within a subgrating region so as to maximize subgrating region area and minimize the number of boundary segments between adjacent subgrating regions. Moreover, it is likely that connection points utilizing the same subgrating will have related or identical functions. Also, in one embodiment, fill shapes neighboring a given subgrating region are placed in accordance with the given subgrating region so as to further maximize the area of the given subgrating region.

When layout shapes are placed according to a subgrating, a situation may arise in which the subgrating pitch and the layout shape width result in a side-to-side spacing between adjacently placed layout shapes that is too large to ensure proper manufacturability of the layout shapes. FIG. 3A shows an example in which a subgrating pitch (SGP) results in a ratio of side-to-side spacing (S1) to layout shape width (W) that is too large to maintain sufficient shape density for proper manufacturing.

FIG. 3B shows a modification of the layout of FIG. 3A in which a subresolution shape 301 is used to mitigate the unacceptably large ratio (S1/W), in accordance with one embodiment of the present invention. The subresolution shape 301 is defined to have a width (SRW) that is small enough to ensure that subresolution shape 301 will not be manufactured. Also, the subresolution shape 301 is placed such that a side-to-side spacing (S2) with its neighboring layout shapes is optimized for manufacturability of the neighboring layout shapes. Also, in some embodiments, because the width (SRW) of the subresolution shape 301 primarily governs whether or not the subresolution shape 301 will actually resolve, i.e., be manufactured, a length (SL) of the subresolution shape 301 can be made as large as necessary without increasing a likelihood that the subresolution shape 301 is inadvertently manufactured. The presence of the subresolution shape 301 will serve to enhance manufacturability of its neighboring layout shapes during a lithographic manufacturing process. It should be understood, however, that subresolution shapes are not intended to be manufactured and should not be placed or sized to cause their manufacture. Moreover, the likelihood of subresolution shape being manufactured can be dependent upon a layout shape density in its surrounding neighborhood. Therefore, the placement and sizing of a given subresolution shape should consider the layout shape density around the given subresolution shape.

In one embodiment, a subresolution shape can be placed within a subgrating region without regard to the corresponding subgrating for the purpose of enhancing manufacturability of layout shapes within the subgrating region. In another embodiment, a subresolution shape can be placed within a subgrating region in accordance with the corresponding subgrating for the purpose of enhancing manufacturability of layout shapes within the subgrating region.

FIG. 4 shows an example layout in which a GPG is used to place layout shapes for gate electrode wires (“gates” hereafter), interconnect wires, diffusion contacts, and gate contacts, in accordance with one embodiment of the present invention. The GPG is defined by virtual lines 401-406 evenly spaced at GPG pitch (GPGP). Gate wires 410 are placed according to a subgrating SG-A within the gate chip level that includes every other even numbered virtual line of the GPG (GPG virtual lines 402, 404, 406), such that the corresponding subgrating pitch is 2*GPGP. Interconnect wires 420 are also placed according to the subgrating SG-A within a given interconnect chip level that includes every other even numbered virtual line of the GPG (GPG virtual lines 402, 404, 406). Interconnect wires 430 are placed according to a subgrating SG-B within the given interconnect chip level that includes every other odd numbered virtual line of the GPG (GPG virtual lines 401, 403, 405), such that the corresponding subgrating pitch is 2*GPGP. Diffusion contacts 440, i.e., source/drain contacts, are also placed according to the subgrating SG-B within the diffusion contact chip level that includes every other odd numbered virtual line of the GPG (GPG virtual lines 401, 403, 405). Gate contacts 450 are placed according to the subgrating SG-A within the gate contact chip level that includes every other even numbered virtual line of the GPG (GPG virtual lines 402, 404, 406).

In one embodiment, layout shapes and subgratings within a portion of a given chip level are defined to enable use of substantially uniform layout shapes widths, substantially uniform layout shape side-to-side spacings, and substantially uniform layout shape end-to-end spacings. For example, the embodiment of FIG. 4 shows use of a substantially uniform interconnect wire layout shape width (M1W) within the illustrated portion of the interconnect chip level. Also, FIG. 4 shows use of a substantially uniform interconnect layout shape side-to-side spacing (M1S) within the illustrated portion of the interconnect chip level. Also, FIG. 4 shows use of a substantially uniform interconnect layout shape end-to-end spacing (M1LES) within the illustrated portion of the interconnect chip level.

Additionally, FIG. 4 shows use of a substantially uniform gate wire layout shape width (GW) within the illustrated portion of the gate chip level. Also, FIG. 4 shows use of a substantially uniform gate layout shape side-to-side spacing (GS) within the illustrated portion of the gate chip level. Also, FIG. 4 shows use of a substantially uniform gate layout shape end-to-end spacing (GLES) within the illustrated portion of the gate chip level. In various embodiments, extension of a layout shape size through stretching of one or more of the layout shape's edges can be used to achieve the substantially constant layout shape widths, side-to-side spacings, and end-to-end spacings. Moreover, although manufacturing benefits (such as in lithography processes) may be achieved by using substantially constant layout shape widths, side-to-side spacings, and end-to-end spacings, it should be understood that use of GPGs, subgratings, and subgrating regions does not require use of substantially constant layout shape widths, side-to-side spacings, and end-to-end spacings.

FIG. 5 shows an extension of the exemplary layout of FIG. 4 in which a number of subgrating regions are defined in various chip levels, in accordance with one embodiment of the present invention. A diffusion level of the exemplary layout includes diffusion regions 502 and 504. A gate level of the exemplary layout includes the gate wire layout shapes 410. A single subgrating region 507 is defined for the gate level, with the subgrating SG-A allocated thereto. Three subgrating regions 501, 503, 505 are defined for each of the diffusion contact level, gate contact level, and interconnect level with the subgratings SG-B, SG-A, SG-B allocated thereto, respectively. Therefore, each of the chip levels of the exemplary layout of FIG. 5 is partitioned into a number of subgrating regions, wherein each of these subgrating regions is defined as a contiguous area within the layout.

FIG. 5 also illustrates how layout shapes of related function can be placed together within a common subgrating region. For example, diffusion contacts 440 and their associated interconnect wires 430 are placed together in each of subgrating regions 501 and 505 in accordance with subgrating SG-B. Also, gate contacts 450 and their associated interconnect wires 420 are placed together in subgrating region 503 in accordance with subgrating SG-A. The gate wires 410 are placed in subgrating region 507 in accordance with subgrating SG-A. Based on the example of FIG. 5, it should be appreciated that allocation of a properly defined subgrating to a given subgrating region provides for placement of layout shapes having a common run length within the given subgrating region.

A layout shape in one subgrating region of a given chip level can connect with another layout shape in an adjacent subgrating region of the given level when the two layout shapes are placed along the same virtual line of the GPG, thereby forming a larger shape that traverses across the interface between the adjacent subgrating regions. This is illustrated above with regard to layout shapes 250A and 250B of FIG. 2 combining to form layout shape 250. Therefore, a layout shape can be defined to cross from one subgrating region to an adjacent subgrating region in a given level when the different subgratings in the adjacent subgrating regions align to a common GPG virtual line.

The techniques described herein may be generalized to enable pattern regularity for any number of chip levels that are partitioned into subgrating regions. FIG. 6 shows an example layout that illustrates subgrating use among different vertically stacked chip levels, in accordance with one embodiment of the present invention. As shown in FIG. 6, a metal-3 subgrating region 620 includes vias 630 that connect to metal-2 wires 631 centered on horizontal GPG virtual line 650. The vias 630 and metal-3 wires 632 that overlap them are centered on odd numbered vertical GPG virtual lines 611, 613, 615, respectively, and have a horizontal pitch M3P2 that is twice the vertical GPG pitch GPG2.

In another metal-3 subgrating region 621, vias 633 that connect to metal-2 wires 634 are centered on horizontal GPG virtual line 651, and the metal-3 wires 635 that overlap them are centered on even numbered vertical GPG virtual lines 610, 612, 614, respectively, and have a horizontal pitch M3P1 that is twice the vertical GPG pitch GPG2.

FIG. 7 shows an example layout in which a multi-level orthogonally routed connection is used to connect wires in a same chip level that cannot have a common run length, in accordance with one embodiment of the present invention. Parallel metal-1 layout shapes 702, 701, 700 are centered on adjacent GPG virtual lines 740, 741, 742, respectively, and have insufficient clearance to run side-by-side, i.e., to have a common run length. Therefore, the metal-1 layout shapes 700, 701, 702 cannot traverse the boundary between the adjacent subgrating regions 760 and 761, and therefore cannot make a physical connection to each other within their chip level.

One solution is to use multiple chip levels with orthogonal routing directions to make the required connections. For example, as shown in FIG. 7, a diffusion shape 704 is connected to gate wire 720 by connecting through each of diffusion contact 710, metal-1 wire 701, via 730, metal-2 wire 740, via 750, metal-3 wire 770, via 751, metal-2 wire 741, via 731, metal-1 wire 702, and contact 711. This multiple chip level orthogonal routing connection solution can be generalized to form connections when layout shapes on a given level cannot traverse a subgrating region boundary that crosses their routing direction, i.e., when layout shapes on a given level cannot have a common run length.

FIG. 8 shows another example layout in which a multi-level orthogonally routed connection is used to connect wires in a same chip level that cannot have a common run length, in accordance with one embodiment of the present invention. Parallel metal-3 wires 800-803 centered on adjacent GPG lines 870-873 cannot traverse the boundary 880 between metal-3 subgrating regions 820 and 821. Therefore, due to the boundary 880, a direct connection cannot be made between metal-3 wires 801 and 802. However, a connection can be made between metal-3 wires 801 and 802 by connecting through each of the following elements: via 830, metal-2 wire 840, via 850, metal-1 wire 860, via 851, metal-2 wire 841, and via 831. FIG. 8 also shows that wires on different levels with identical routing directions such as metal-1 wires 860-862 and metal-3 wires 800-803 may be centered on different GPGs such as the GPG with pitch GRM3 for metal-3 and the GPG with pitch GRM1 for metal-1.

In one embodiment, the GPG and subgrating region techniques described above can be used to enforce the following layout shape pattern regularity conventions that are beneficial to manufacturing: 1) layout shapes are rectangular, i.e., linear-shaped, 2) wire layout shape pitch is substantially constant in the direction orthogonal to routing, 3) contact layout shape pitch is substantially constant in the direction orthogonal to routing, 4) wire layout shape width is substantially constant, 5) wire layout shape side-to-side spacing is substantially constant, 6) wire layout shape end-to-end spacing is substantially constant, and 7) overall layout shape density is as uniform as possible.

FIG. 9A shows an example layout that illustrates the occurrence of a non-standard spacing at an interface between adjacent subgrating regions, in accordance with one embodiment of the present invention. In the example of FIG. 9A, a metal-1 subgrating region 900 that includes gate contacts 940 centered on even numbered GPG lines 924, 926, and a metal-1 subgrating region 901 that includes diffusion contacts 950 centered on odd GPG lines 921, 923. The metal-1 subgrating region 901 borders the metal-1 subgrating region 900 both vertically and horizontally. This introduces a non-standard spacing, M1S2, straddling the horizontal subgrating regional border located between the metal-1 wires 910 and 912.

FIG. 9B shows a layout shape stretching technique for mitigating a non-standard spacing introduced at subgrating region borders that lie parallel to the routing direction, in accordance with one embodiment of the present invention. The layout of FIG. 9B is a modified version of the metal-1 layout of FIG. 9A. In FIG. 9B, the edge of metal-1 wire 910 that faces the large gap is stretched until it is co-linear with the edge of a metal-1 wire 911, which faces the same gap but is centered on an alternate grating line 923. By stretching the metal-1 wire 910, wire spaces M1S are made constant, but the metal-1 wire 910 has non-standard width and is no longer centered on a GPG line. However, the stretching of the metal-1 wire 910 in favor of constant spacing provides an overall improvement in manufacturability.

FIG. 10A shows an example layout that illustrates the occurrence of a non-standard spacing at an interface between adjacent subgrating regions, when the layout shape stretching technique of FIG. 9B is blocked, in accordance with one embodiment of the present invention. In FIG. 10A, layout shape 1010 in subgrating region 1000 runs parallel to a layout shape 1012 in subgrating region 1001, wherein layout shapes 1010 and 1012 are aligned to different subgratings. The non-standard gap M1S2 extends along the common run length CRL of layout shapes 1010 and 1012. The layout shape 1010 cannot be stretched toward the layout shape 1012 to reduce M1S2 because it is blocked by another layout shape 1013 in the same subgrating region 1000.

Due to the application of a GPG and fixed layout shape widths, M1S2 is most likely limited to a fixed value. In the example of FIG. 10A, M1S2=3*GPGP−M1W. More specifically, the fixed value for M1S2 applies to regions of the chip that share the same GPGP and M1W values. Thus, it should be appreciated that even when non-standard gaps, e.g., M1S2, cannot be mitigated through layout shape modification (such as layout shape stretching), specification of a constant GPGP value and of a limited number of layout shape widths, e.g., M1W, will serve to limit the corresponding number of non-standard gap values that may occur in the layout. For instance, in the example of FIG. 10A, use of the constant GPGP value and the single layout shape width M1W serves to limit the number of non-standard gap values to one, i.e., to the M1S2 value. Therefore, through specification of a constant GPGP value and of a limited number of layout shape widths it is possible to optimize manufacturing processes to account for a controlled number of non-standard spacings that may occur in the layout. In contrast, it should be appreciated that such manufacturing process optimization is not feasible when an uncontrolled number of non-standard layout shape spacings may occur in a given layout.

FIG. 10B illustrates use of a subresolution shape to mitigate a non-standard spacing at an interface between adjacent subgrating regions, as an alternative to the layout shape stretching technique of FIG. 9B is blocked, in accordance with one embodiment of the present invention. The layout of FIG. 10B is a modified version of the layout of FIG. 10A. In FIG. 10B, a sub-resolution layout shape 1014 is placed within the area corresponding to the non-standard spacing. As with the previous subresolution layout shape description of FIG. 3B, a width (SRW) of the subresolution layout shape 1014 should be small enough to ensure that the subresolution layout shape 1014 is not manufactured. It should be appreciated that overall layout shape density and layout shape side-to-side spacing M1S can be made substantially uniform through use of this subresolution layout shape insertion technique. It should be understood, however, that in some embodiments the presence of a non-standard spacing at subgrating region boundaries is acceptable and does not require mitigation.

FIG. 11 shows an exemplary layout in which a layout shape is stretched to overlap multiple contacts and/or vias, in accordance with one embodiment of the present invention. In one embodiment, a linear layout shape of a wire can be stretched orthogonally to its preferred routing direction so that it overlaps multiple contacts and/or vias. For example, FIG. 11 shows a metal-1 wire 1110 having a preferred horizontal routing direction, i.e., preferred x-direction of routing. The metal-1 wire 1110 is placed in a subgrating region 1100 that is defined adjacent to a subgrating region 1103. The metal-1 wire 1110 needs to connect to each of contacts 1120 and 1121. While the metal-1 wire 1110 may have been initially placed in a centered manner on a GPG virtual line, the metal-1 wire 1110 is stretched orthogonal to its preferred routing direction, i.e., is stretched in the y-direction, so as to cover both of contacts 1120 and 1121. It should be understood that the linear layout shape stretching technique, exemplified by the metal-1 wire 1110 of FIG. 11, can be generalized to facilitate connection of layout shapes within different chip levels, within different subgrating regions of a given chip level, or within a same subgrating region of a given chip level.

FIG. 12 shows another example in which layout shapes are stretched to overlap multiple contacts and/or vias, in accordance with one embodiment of the present invention. In FIG. 12, a metal-2 wire layout shape 1231 is stretched in the x-direction, i.e., widened, such that both of its edges maintain a standard spacing M2S to adjacent wire layout shapes 1232 and 1233, and such that it overlaps and connects with a via 1240 and a via 1241. In this manner, the metal-2 wire 1231 serves to connect a metal-3 wire 1261 in a metal-3 subgrating region 1270 to a metal-3 wire 1262 in a metal-3 subgrating region 1271. Also, a metal-2 wire layout shape 1230 is similarly widened to overlap and connect with a via 1250 and a via 1242, which are respectively connected to a metal-1 wire 1220 and a metal-3 wire 1260.

FIG. 13 shows an example in which layout shapes are extended relative to a contact and/or via so as to accommodate design requirements, in accordance with one embodiment of the present invention. Two adjacent subgrating regions 1300 and 1301 are defined for a metal-1 chip level. A diffusion contact 1311 is defined to connect a diffusion region 1323 to a metal-1 wire 1321. The diffusion contact 1311 is covered by the metal-1 wire 1321 layout shape. Given a lack of metal-1 wire 1321 overlap of the contact 1311 in the y-direction, a horizontal extension M1OL of the metal-1 wire 1321 layout shape in the x-direction is provided to enable compliance with design rules. Also, a gate contact 1310 is defined to connect a gate wire 1322 to a metal-1 wire 1320. The metal-1 wire 1320 layout shape can be defined to minimally overlap the gate contact 1310 in the x-direction due to the significant overlap of the gate contact 1310 by the metal-1 wire 1320 layout shape in the y-direction.

It should be understood that the manufacturability benefits of layout techniques described herein are preserved if dimensions referred to as substantially constant are allowed to vary slightly, so long as general layout pattern regularity is preserved. In one embodiment, the following layout method can be used for chip levels that are to be routed according to a GPG that is defined by a pitch too small to allow for common run lengths of shapes placed on adjacent GPG virtual lines. First, subgratings are defined. In one embodiment, alternate GPG lines are used for alternate functions when defining the subgratings. Then, layout shapes are organized according to subgrating regions. In one embodiment, layout shapes that use the same set of GPG virtual lines are grouped together in subgrating regions. Multiple chip levels can be utilized to make connections between layout shapes of a given chip level when required due to fragmentation of those layout shapes at subgrating region boundaries within the given chip level.

Additionally, after initial layout shape placement, layout shapes can be stretched, i.e., widened, so as to maintain substantially constant side-to-side spacing where necessary, such as at subgrating region boundaries that run parallel to the preferred routing direction. In some instances, non-standard spaces between layout shapes at subgrating region boundaries can be accepted when those non-standard spaces are predictable and fixed. Also, in some instances, non-standard spaces between layout shapes at subgrating region boundaries can be partially filled using subresolution layout shapes. Moreover, in some instances, layout shapes neighboring non-standard spaces at subgrating region boundaries can be stretched so as to mitigate the non-standard spaces. Furthermore, a layout shape can be stretched, i.e., widened, in the direction orthogonal to its preferred routing direction so as to allow for connection of multiple overlapping contacts and/or vias to the layout shape. Also, a layout shape can be stretched, i.e., widened, in the direction orthogonal to its preferred routing direction so as to allow for reduction of contact and/or via overlap/extension by the layout shape in the direction parallel to its preferred routing direction.

FIG. 14 shows a flowchart of a method for defining a layout for a portion of a given semiconductor chip level, in accordance with one embodiment of the present invention. The method includes an operation 1401 for defining a preferred routing direction for a given chip level. The method also includes an operation 1403 for identifying each contact level related to the given chip level, wherein such a related contact level includes at least one interfacing contact defined to physically connect with a structure corresponding to a layout shape to be placed in the given chip level. In various embodiments, contact levels related to the given chip level can include a gate contact level, a diffusion contact level, a via level, or a combination thereof.

The method further includes an operation 1405 for defining a global placement grating (GPG) for the given chip level to include a set of parallel and evenly spaced virtual lines. The GPG is defined such that at least one virtual line of the GPG is positioned to intersect each interfacing contact within each contact level that is related to the given chip level, as identified in operation 1403. An operation 1407 is then performed to determine whether a perpendicular spacing between adjacent virtual lines of the GPG, i.e., GPG pitch, provides for enforcement of layout shape pattern regularity within the given chip level as necessary to ensure manufacturability of layout shapes within the given chip level.

It should be understood that what constitutes sufficient layout shape pattern regularity can be dependent upon many factors, such as a critical dimension of structures to be defined in the chip, a spacing between structures to be defined in the chip, and/or a function of structures to be defined in the chip, among others. Thus, it should be understood that what constitutes sufficient layout shape pattern regularity can vary from one design to another. In one particular embodiment, enforcement of layout shape pattern regularity within a given chip level includes one or more of 1) a substantially constant layout shape width as measured perpendicular to the preferred routing direction, 2) a substantially constant spacing between adjacently placed layout shapes as measured perpendicular to the preferred routing direction, and 3) a substantially constant spacing between ends of adjacently placed layout shapes as measured parallel to the preferred routing direction. An example of this embodiment is illustrated in FIG. 4, as previously described.

If operation 1407 determines that the perpendicular spacing between adjacent virtual lines of the global placement grating is not acceptable, the method proceeds with an operation 1411 for adjustment of the placement(s) of one or more contacts that interface with the given chip level. Then, the method reverts back to operation 1405 and proceeds as described above.

If operation 1407 determines that the perpendicular spacing between adjacent virtual lines of the global placement grating is acceptable, the method proceeds with an operation 1409 in which layout shapes are placed in alignment with the GPG for the given chip level. In one embodiment, the layout shapes placed in alignment with the GPG are defined as linear layout shapes having a substantially rectangular cross-section when viewed in an as-drawn state. Also, in one embodiment, each linear layout shape is placed such that a length of its substantially rectangular cross-section is parallel with the preferred routing direction. Additionally, in one embodiment, each linear layout shape is initially placed such that its centerline extending in the preferred routing direction is substantially centered upon a virtual line of the GPG. It stood be understood, however, that after initial placement, some of the linear layout shapes may be stretched or otherwise modified to mitigate non-standard spacings within the layout so as to provide for sufficient layout shape pattern regularity as necessary to ensure manufacturability of layout shapes within the given chip level.

FIG. 15A shows a flowchart of a method for defining a layout for a portion of a given semiconductor chip level, in accordance with one embodiment of the present invention. The method includes an operation 1501 for defining a global placement grating (GPG) for a given chip level. The GPG is defined by a set of parallel and evenly spaced virtual lines. The method also includes an operation 1503 for identifying all connection lines within the GPG. A connection line is a virtual line of the GPG that is spatially coincident with a virtual line of a related contact level. A related contact level includes at least one contact that is defined to physically connect with a structure corresponding to a layout shape placed within the given chip level. The virtual lines of any given related contact level are defined as a set of parallel and equally spaced virtual lines to which contact layout shapes are aligned.

The method further includes an operation 1505 for defining a subgrating for the given chip level. A subgrating is defined as a set of evenly spaced connection lines, such that a spacing between adjacent connection lines in the subgrating is at least as large as a minimum spacing required to support a common run length of layout shapes on the adjacent connection lines in the subgrating. A common run length of two layout shapes occurs where the two layout shapes are placed in a side-by-side manner on adjacent connection lines in the subgrating. In one embodiment, defining a subgrating for a chip level includes associating the subgrating with a particular function to be performed by structures corresponding to layout shapes to be placed in accordance with the given subgrating. Also, in this embodiment, a perpendicular spacing between adjacent lines of the given subgrating is defined to accommodate placement of the layout shapes corresponding to the particular function.

Following operation 1505, the method proceeds with a decision operation 1507 for determining whether each connection line within the global placement grating is associated with at least one subgrating. If each connection line is not associated with at least one subgrating the method reverts back to proceed again with operation 1505. However, if each connection line is associated with at least one subgrating, the method proceeds with operation 1509 for placing layout shapes in alignment with the defined subgratings, such that each layout shape is associated with any one subgrating.

In one embodiment, each layout shape of the given chip level is placed in alignment with at least one subgrating for the given chip level and is defined as a linear layout shape having a substantially rectangular cross-section when viewed in an as-drawn state. Each linear layout shape is placed such that its lengthwise centerline extends parallel to the virtual lines of the GPG. Also, each linear layout shape is initially placed such that its lengthwise centerline is substantially centered upon a line of its subgrating.

FIG. 15B shows an expanded view of operation 1509, in accordance with one embodiment of the present invention. In an operation 1511, the layout for the given chip level is partitioned into a number of subgrating regions. Each subgrating region is defined as a contiguous area within the layout for the given chip level. An operation 1513 is performed to allocate subgratings to the number of subgrating regions, such that only one subgrating is allocated to any one subgrating region. It should be understood, however, that different subgrating regions can have different subgratings respectively allocated thereto. In one embodiment, each of the number of subgrating regions within the given chip level is defined such that a layout area of each subgrating region is made as large as possible while accommodating layout area requirements of every other subgrating region within the given chip level. Also in this embodiment, the subgrating regions within the given chip level are defined such that a minimal number of boundary segments are used to define a periphery of each subgrating region.

Once the subgrating regions are defined and have subgratings allocated thereto, the method proceeds with an operation 1515 for placing a first set of layout shapes for the given chip level. Each layout shape of the first set is aligned to the subgrating for the subgrating region in which the layout shape is placed. In one embodiment, each layout shape of the given chip level is placed according to the following specifications: 1) the layout shape is placed in alignment with at least one subgrating for the given chip level and is defined as a linear layout shape having a substantially rectangular cross-section when viewed in an as-drawn state, 2) the layout shape is placed such that its lengthwise centerline extends parallel to the virtual lines of the GPG, 3) the layout shape is initially placed such that its lengthwise centerline is substantially centered upon a line of its subgrating.

In one augmentation of the above-described embodiment, a particular linear layout shape of the given chip level is stretched in its widthwise direction extending perpendicular to the virtual lines of the GPG, after the initial placement of the particular linear layout shape, such that a structure corresponding to the particular linear layout shape will physically connect with multiple contacts (i.e., contacts and/or vias) within one or more related contact levels. An example of this is illustrated in FIG. 11 by the stretching of layout shape 1110 to cover and physically connect with contacts 1120 and 1121. In another augmentation of the above-described embodiment, a particular linear layout shape of the given chip level is stretched in its widthwise direction extending perpendicular to the virtual lines of the GPG, after the initial placement of the particular linear layout shape, such that a structure corresponding to the particular linear layout shape will sufficiently overlap one or more contacts (i.e., contacts and/or vias) within one or more related contact levels. An example of this is illustrated in FIG. 13 by the stretching of layout shape 1320 to sufficiently overlap contact 1310.

Additionally, in one embodiment, some layout shapes in adjacent subgrating regions that are placed on a common virtual line of the GPG are extended through a boundary between the adjacent subgrating regions so as to faun a single contiguous layout shape. In yet another embodiment, two or more layout shapes respectively placed in adjacent subgrating regions of the given chip level and on different virtual lines of the GPG are electrically connected together by orthogonally routed structures that extend through multiple chip levels. In this embodiment, the subgratings of the adjacent subgrating regions may not accommodate a common run length of the two or more layout shapes.

FIG. 15C shows an extension of the method of FIGS. 15A-15B, in accordance with various embodiments of the present invention. In one embodiment, the method proceeds from operation 1515 with an operation 1517 for identifying a blank space within the layout of the given chip level. The blank space in this embodiment is identified as a spatial area within the layout of the given chip level at which a non-standard spacing exists between layout shapes of the first set as placed in operation 1515. The method then proceeds with an operation 1519 for identifying a subgrating associated with a neighboring layout shape of the first set relative to the blank space and proximate to the blank space. An operation 1521 is then performed to define a second set of layout shapes for the given chip level within the blank space. The second set of layout shapes are placed in alignment with the subgrating identified in operation 1519. The second set of layout shapes are defined within the blank space so as to optimize manufacturability of the first set of layout shapes. In one embodiment, operations 1517 through 1521 are repeated until each blank space within the given chip level has been considered for placement of one or more layout shapes of the second set therein.

In another embodiment, the method proceeds from operation 1515 with an operation 1525 for identifying a non-standard spacing within the layout of the given chip level at an interface between adjacent subgrating regions. The method then proceeds with an operation 1527 for identifying a layout shape adjacent to the non-standard spacing that can be stretched toward the interface between the adjacent subgrating regions. An operation 1529 is then performed to stretch the layout shape identified in operation 1527 toward the interface between the adjacent subgrating regions so as to mitigate the non-standard spacing. In one embodiment, the layout shape identified in operation 1527 is stretched within its subgrating region so as to align with another layout shape present in the adjacent subgrating region. In one embodiment the layout shape identified in operation 1527 is a linear layout shape and is stretched in its widthwise direction that extends perpendicular to the virtual lines of the GPG.

In yet another embodiment, the method proceeds from operation 1515 with an operation 1531 for identifying a non-standard spacing within the layout of the given chip level at an interface between adjacent subgrating regions. The method then proceeds with an operation 1533 for identifying an inability to stretch a layout shape adjacent to the non-standard spacing toward the interface between the adjacent subgrating regions. An operation 1535 is then performed to define a subresolution layout shape within a layout area of the given chip level corresponding to the non-standard spacing. The subresolution shape is defined to reinforce manufacturability of the first set of layout shapes near the non-standard spacing, and so as to ensure that the subresolution layout shape is not manufactured.

In yet another embodiment, following operation 1515, one or more non-standard spacings are identified within the layout of the given chip level. In this embodiment, a decision is made to not mitigate the identified non-standard spacings. For example, the identified non-standard spacings may be dealt with through optimization of one or more manufacturing processes without requiring modification of the layout of the given chip level.

FIG. 16 shows a flowchart of a method for defining a layout for a portion of a given semiconductor chip level, in accordance with one embodiment of the present invention. The method includes an operation 1601 for defining a global placement grating (GPG) for a given chip level, wherein the global placement grating is defined by a set of parallel and evenly spaced virtual lines. The method also includes an operation 1603 for identifying all connection lines within the GPG. A connection line is a virtual line of the GPG that is spatially coincident with a virtual line of a related contact level. The method further includes an operation 1605 for defining a subgrating for the given chip level as a set of evenly spaced connection lines, such that a spacing between adjacent connection lines in the subgrating is at least as large as a minimum spacing required to support a common run length of layout shapes on the adjacent connection lines in the subgrating.

A decision operation 1607 is provided to determine whether or not each connection line within the GPG is associated with at least one subgrating. If each connection line within the GPG is not associated with at least one subgrating, the method reverts back to operation 1605. If each connection line within the GPG is associated with at least one subgrating, the method continues with an operation 1609 for partitioning the layout for the given chip level into a number of subgrating regions. Each subgrating region is defined as a contiguous area within the layout for the given chip level. An operation 1611 is then performed to allocate subgratings to the number of subgrating regions such that only one subgrating is allocated to any one subgrating region. It should be understood that different subgratings can be allocated to different subgrating regions, so long as no more than one subgrating is allocated to a given subgrating region in a given chip level.

The method continues with an operation 1613 for placing functional layout shapes for the given chip level in alignment to the subgratings allocated to the subgrating regions. Following placement of the functional layout shapes in operation 1613, the method proceeds with an operation 1615 for identifying a non-standard spacing within the layout of the given chip level. In one embodiment, identifying the non-standard spacing in operation 1615 includes comparing a side-to-side spacing of functional layout shapes located adjacent to each subgrating region interface extending parallel to the virtual lines of the GPG with a standard side-to-side spacing between (or specified for) adjacent functional layout shapes within the given chip level.

In one embodiment, an operation 1617 is then performed to resolve the non-standard spacing so as to optimize manufacturability of structures corresponding to the functional layout shapes. In various embodiments, resolving the non-standard spacing in operation 1617 can include either stretching a functional layout shape to reduce the non-standard spacing, or inserting a non-functional layout shape within the non-standard spacing, or inserting a subresolution shape within the non-standard spacing, or a combination thereof.

In an alternative embodiment, operation 1617 includes making a decision to not mitigate the identified non-standard spacing. For example, the identified non-standard spacing may be dealt with through adjustment of one or more manufacturing processes without requiring modification of the layout of the given chip level.

In one embodiment, each functional layout shape of the given chip level is placed in alignment with at least one subgrating for the given chip level and is defined as a linear layout shape having a substantially rectangular cross-section when viewed in an as-drawn state. Also in this embodiment, each functional layout shape is placed such that its lengthwise centerline extends parallel to the virtual lines of the GPG. Also in this embodiment, each functional layout shape is initially placed (prior to operation 1617) such that its lengthwise centerline is substantially centered upon a line of its subgrating.

It should be understood that the chip layouts generated by the methods disclosed herein can be stored in a tangible form, such as in a digital format on a computer readable medium. Also, the invention described herein can be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include hard drives, network attached storage (NAS), read-only memory, random-access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and other optical and non-optical data storage devices. The computer readable medium can also be distributed over a network of coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

Any of the operations described herein that form part of the invention are useful machine operations. The invention also relates to a device or an apparatus for perfoiming these operations. The apparatus may be specially constructed for the required purpose, such as a special purpose computer. When defined as a special purpose computer, the computer can also perform other processing, program execution or routines that are not part of the special purpose, while still being capable of operating for the special purpose. Alternatively, the operations may be processed by a general purpose computer selectively activated or configured by one or more computer programs stored in the computer memory, cache, or obtained over a network. When data is obtained over a network the data maybe processed by other computers on the network, e.g., a cloud of computing resources.

The embodiments of the present invention can also be defined as a machine that transforms data from one state to another state. The data may represent an article, that can be represented as an electronic signal and electronically manipulate data. The transformed data can, in some cases, be visually depicted on a display, representing the physical object that results from the transformation of data. The transformed data can be saved to storage generally, or in particular formats that enable the construction or depiction of a physical and tangible object. In some embodiments, the manipulation can be performed by a processor. In such an example, the processor thus transforms the data from one thing to another. Still further, the methods can be processed by one or more machines or processors that can be connected over a network. Each machine can transform data from one state or thing to another, and can also process data, save data to storage, transmit data over a network, display the result, or communicate the result to another machine.

While this invention has been described in terms of several embodiments, it will be appreciated that those skilled in the art upon reading the preceding specifications and studying the drawings will realize various alterations, additions, permutations and equivalents thereof. Therefore, it is intended that the present invention includes all such alterations, additions, permutations, and equivalents as fall within the true spirit and scope of the invention. 

What is claimed is:
 1. A method for defining a layout for a portion of a given semiconductor chip level, comprising: (a) defining a preferred routing direction for a portion of a given chip level; (b) operating a computer to identify each contact level related to the portion of the given chip level, wherein each contact level related to the portion of the given chip level includes at least one interfacing contact defined to physically connect with a structure corresponding to a layout shape to be placed in the portion of the given chip level; (c) operating the computer to define a placement grating for the portion of the given chip level to include a set of parallel and evenly spaced virtual lines, whereby at least one virtual line of the placement grating is positioned to intersect each interfacing contact within each contact level related to the portion of the given chip level; (d) operating the computer to determine whether a perpendicular spacing between adjacent virtual lines of the placement grating provides for enforcement of layout shape pattern regularity within the portion of the given chip level as necessary to ensure manufacturability of layout shapes within the portion of the given chip level; and (e) if operation (d) determines that the perpendicular spacing between adjacent virtual lines of the placement grating is acceptable, operating the computer to allow placement of layout shapes in alignment with the placement grating for the portion of the given chip level, or if operation (d) determines that the perpendicular spacing between adjacent virtual lines of the placement grating is not acceptable, operating the computer to adjust placement of one or more interfacing contacts within one or more contact levels related to the portion of the given chip level and then repeat operations (c) through (e).
 2. The method of claim 1, wherein the layout shapes placed in alignment with the placement grating are defined as linear layout shapes having a substantially rectangular cross-section.
 3. The method of claim 2, wherein each linear layout shape is placed such that a length of its substantially rectangular cross-section is parallel with the preferred routing direction.
 4. The method of claim 2, wherein each linear layout shape is initially placed such that its centerline extending in the preferred routing direction is substantially centered upon a virtual line of the placement grating.
 5. The method of claim 4, further comprising: adjusting a width of a given linear layout shape as measured perpendicular to the preferred routing direction following initial placement of the given linear layout shape.
 6. The method of claim 5, wherein the width of the given linear layout shape is adjusted such that the centerline of the given linear layout shape extending in the preferred routing direction remains substantially centered upon the virtual line of the placement grating.
 7. The method of claim 6, wherein the width of the given linear layout shape is adjusted to maintain a substantially uniform side-to-side spacing as measured perpendicular to the preferred routing direction between adjacently positioned linear layout shapes.
 8. The method of claim 5, wherein the width of the given linear layout shape is adjusted such that the centerline of the given linear layout shape extending in the preferred routing direction is not centered upon the virtual line of the placement grating.
 9. The method of claim 8, wherein the width of the given linear layout shape is adjusted to maintain a substantially uniform side-to-side spacing as measured perpendicular to the preferred routing direction between adjacently positioned linear layout shapes.
 10. The method of claim 1, wherein contact levels related to the portion of the given chip level include one or more of a gate contact level, a diffusion contact level, and a via level.
 11. The method of claim 1, wherein enforcement of layout shape pattern regularity within the portion of the given chip level includes one of more of requiring a substantially constant layout shape width as measured perpendicular to the preferred routing direction, requiring a substantially constant spacing between adjacently placed layout shapes as measured perpendicular to the preferred routing direction, and requiring a substantially constant spacing between ends of adjacently placed layout shapes as measured parallel to the preferred routing direction.
 12. The method of claim 1, wherein operating the computer to determine whether the perpendicular spacing between adjacent virtual lines of the placement grating provides for enforcement of layout shape pattern regularity within the portion of the given chip level as necessary to ensure manufacturability of layout shapes within the portion of the given chip level includes verifying that the perpendicular spacing between adjacent virtual lines of the placement grating accommodates a side-by-side existence of layout shapes on adjacent virtual lines of the placement grating.
 13. The method of claim 12, wherein the layout shapes having the side-by-side existence on adjacent virtual lines of the placement grating have a uniform width as measured perpendicular to the preferred routing direction.
 14. The method of claim 1, wherein the placement grating for the portion of the given chip level is a subgrating of a global placement grating, the global placement grating extending beyond the portion of the given chip level.
 15. The method of claim 14, wherein a distance between adjacent virtual lines of the subgrating as measured perpendicular to the preferred routing direction is a subgrating pitch, and a distance between adjacent virtual lines of the global placement grating as measured perpendicular to the preferred routing direction is a global placement grating pitch, the subgrating pitch larger than the global placement grating pitch.
 16. The method of claim 15, wherein the subgrating pitch is an integer multiple of the global placement grating pitch.
 17. The method of claim 1, wherein the given chip level is an interconnect level formed above a gate level.
 18. The method of claim 1, wherein the given chip level is a gate level.
 19. A data storage device having program instructions stored thereon for defining a layout for a portion of a given semiconductor chip level, comprising: program instructions for defining a preferred routing direction for a portion of a given chip level; program instructions for identifying each contact level related to the portion of the given chip level, wherein each contact level related to the portion of the given chip level includes at least one interfacing contact defined to physically connect with a structure corresponding to a layout shape to be placed in the portion of the given chip level; and program instructions for generating a placement grating for the portion of the given chip level by, (a) defining a placement grating for the portion of the given chip level to include a set of parallel and evenly spaced virtual lines, whereby at least one virtual line of the placement grating is positioned to intersect each interfacing contact within each contact level related to the portion of the given chip level; (b) determining whether a perpendicular spacing between adjacent virtual lines of the placement grating provides for enforcement of layout shape pattern regularity within the portion of the given chip level as necessary to ensure manufacturability of layout shapes within the portion of the given chip level; and (c) if operation (b) determines that the perpendicular spacing between adjacent virtual lines of the placement grating is acceptable, allowing placement of layout shapes in alignnient with the placement grating for the portion of the given chip level, or if operation (b) determines that the perpendicular spacing between adjacent virtual lines of the placement grating is not acceptable, adjusting placement of one or more interfacing contacts within one or more contact levels related to the portion of the given chip level and then repeating operations (a) through (c).
 20. The data storage device as recited in claim 19, wherein enforcement of layout shape pattern regularity within the portion of the given chip level includes one of more of requiring a substantially constant layout shape width as measured perpendicular to the preferred routing direction, requiring a substantially constant spacing between adjacently placed layout shapes as measured perpendicular to the preferred routing direction, and requiring a substantially constant spacing between ends of adjacently placed layout shapes as measured parallel to the preferred routing direction. 